richard engel saw it firsthand, standing by in cairo tonight, good evening, richard. >> reporter: good evening, brian, the egyptian president, mohamed morsy, supporters of the muslim brotherhood want a strong president and want more islamic law. his opponents say the president is forcing an islamic agenda down their throat. and today, the two sides clashed. on the door step of egypt's presidential palace, leading clashes, the fighting injured hundreds. the fighting is very fluid, sometimes the anti-morsy demonstrators, those right here will make advances just a few yards then get driven back. there are no police here, they are just two sides facing each other in the streets. as one side advances the other retreats. demonstrators kept police from the scene. there is still mistrust here, during the revolution of hosni mubarak. >> when the egyptian people go out again in the streets, they never go back. they must win, otherwise the muslim brotherhood will destroy egypt. >> reporter: a battle for the soul of the biggest country in the arab word. and tonight, brian, four of president morsy'